Multilayer structures that include biaxially oriented films and sealant layers and methods for making the same

Abstract

According to one or more embodiments presently disclosed herein, a multilayer structure may include a biaxially oriented film and a sealant layer. The biaxially oriented film may include at least 90% by weight of polypropylene. The sealant layer may be on the biaxially oriented polypropylene film. The sealant layer may include from 15 to 40 percent by weight of a low density polyethylene based on the total weight of the sealant layer. The sealant layer may additionally include from 60 to 85 percent by weight of a propylene-based plastomer based on the total weight of the sealant layer. The propylene-based plastomer may have a density of 0.890 g/cm3 or less and a melt flow rate (at 230° C. and 2.16 kg) of at least 8 g/10 minutes.

1 . A multilayer structure comprising:
 a biaxially oriented film comprising at least 90% by weight of polypropylene; and   a sealant layer on the biaxially oriented polypropylene film, wherein the sealant layer comprises:
 from 15 wt. % to 40 wt. % of a low density polyethylene based on the total weight of the sealant layer; and 
 from 60 wt. % to 85 wt. % of a propylene-based plastomer based on the total weight of the sealant layer, wherein the propylene-based plastomer has a density of 0.890 g/cm 3  or less and a melt flow rate (at 230° C. and 2.16 kg) of at least 8 g/10 minutes. 
   
     
     
         2 . The multilayer structure of  claim 1 , wherein the sealant layer comprises from 15 wt. % to 30 wt. % of the low density polyethylene based on the total weight of the sealant layer. 
     
     
         3 . The multilayer structure of  claim 1 , wherein the sealant layer is extruded on the biaxially oriented polypropylene film. 
     
     
         4 . The multilayer structure of  claim 1 , wherein the low density polyethylene of the sealant layer has a molecular weight distribution (Mw/Mn) of from 7 to 13. 
     
     
         5 . The multilayer structure of  claim 1 , wherein the low density polyethylene of the sealant layer has a melt index (I 2 ) of from 1.5 to 9. 
     
     
         6 . The multilayer structure of  claim 1 , wherein the propylene-based plastomer has a melt flow rate (at 230° C. and 2.16 kg) of from 8 g/10 minutes to 35 g/10 minutes. 
     
     
         7 . The multilayer structure of  claim 1 , wherein the propylene-based plastomer is a copolymer comprising units of propylene and ethylene. 
     
     
         8 . The multilayer structure of  claim 7 , wherein the propylene-based plastomer has an ethylene content of from 2 mol. % to 12 mol. %. 
     
     
         9 . The multilayer structure of  claim 1 , wherein the propylene-based plastomer has a melting point of from 50° C. to 120° C. 
     
     
         10 . The multilayer structure of  claim 1 , wherein the propylene-based plastomer has a melt index of from 20 g/10 minutes to 30 g/10 minutes. 
     
     
         11 . The multilayer structure of  claim 1 , wherein the biaxially oriented film is in direct contact with the sealant layer. 
     
     
         12 . A method for forming a multilayer structure, the method comprising:
 extruding a sealant layer directly onto a biaxially oriented film at an elevated temperature; and   cooling at least the sealant layer;   
       wherein:
 the biaxially oriented film comprises at least 90% by weight of polypropylene; and 
 the sealant layer comprises:
 from 15 wt. % to 40 wt. % of a low density polyethylene based on the total weight of the sealant layer; and 
 from 60 wt. % to 85 wt. % of a propylene-based plastomer based on the total weight of the sealant layer, wherein the propylene-based plastomer has a density of 0.890 g/cm 3  or less and a melt flow rate (at 230° C. and 2.16 kg) of at least 8 g/10 minutes. 
 
 
     
     
         13 . The method of  claim 12 , wherein the elevated temperature is less than or equal to 120° C. 
     
     
         14 . The method of  claim 12 , wherein the elevated temperature is less than or equal to 100° C. 
     
     
         15 . The method of  claim 12 , wherein the elevated temperature is less than or equal to 90° C.